Process for preparing cyclohexanediones-(1,3)

ABSTRACT

Process for preparing cyclohexanediones-(1,3) by reaction of a gamma -acylcarboxylic acid ester with a strongly basic condensing agent, in the presence of a solvent consisting essentially of carboxylic acid amides, phosphoric acid amides, sulfoxides, sulfones or macrocyclic polyethers.

United States Patent Muller 1 Nov. 25, 1975 PROCESS FOR PREPARING CYCLOHEXANEDlONES-( 1,3)

Werner H. Miiller, Kelkheim, Taunus. Germany Hoechst Aktiengesellschaft, Frankfurt am Main, Germany Filed: Sept. 13, 1973 Appl. No.: 396,983

Inventor:

Assignee:

Foreign Application Priority Data Sept. I5. 1972 Germany 2245270 U.S. Cl. 260/586 C; 260/590 C07C 45/00 Field of Search 260/586 R, 590

References Cited UNITED STATES PATENTS 7/1971 Hofmann et ul. 260/586 R X OTHER PUBLICATIONS Vorlander et al., Justus Liebgs Annalen du Chemie,

Bornstern et al., Chem. Abstract" Vol. 48. p. 9933e (1954).

Kost et al.. Zhurnal Obshch Khim" Vol. 32, pp. 3983-3986. (1962) cited in CA. 58213808d.

Mannich et al., Berichte 71, pp. 2090-2091, (1938).

Primary Examiner-N0rman P. Morgenstern Attorney. Agent, or FirmCurtis, Morris & Safford [57] ABSTRACT Process for preparing cyclohexanediones-(l,3) by reaction of a 'y-acylcarboxylic acid ester with a strongly basic condensing agent, in the presence of a solvent consisting essentially of carboxylic acid amides, phosphoric acid amides, sulfoxides, sulfones or macrocyclic polyethers.

11 Claims, No Drawings PROCESS FOR PREPARING CYCLOHEXANEDIONES-( 1,3)

It is well known that cyclohexanediones-( 1,3) can be prepared by cyclization of the corresponding ketocarboxylic acid esters with sodium alcoholates in diethyl ether or methanol.

These methods have the following drawbacks poor selectivity, insufficient space time-yields and difficult 1O 12 R a as 4 ll. H 0

wherein the individual radicals R may be identical or different and represent each a hydrogen atom, an alkyl group or an aryl group, by reaction of a 'y-acyl carboxylic acid ester having the formula wherein R has the aforesaid meaning, and wherein R is an alkyl or an aryl group with a strongly basic condensing agent in presence of a solvent, containing at least 50 7c of a compound belonging to the following classes:

a. carboxylic acid amides having the formula wherein the individual radicals R may be identical or different, meaning each a hydrogen atom, an alkyl group or an aryl group,

b. phosphoric acid amides having the formula wherein the individual radicals R may be identical or different, meaning each an alkyl group or an aryl group,

0. sulfoxides and sulfones having the formulae wherein the individual radicals R may be identical or different, meaning each an alkyl group or an aryl group, and

d. macrocylic polyethers. As condensing agents may be used the strongly basic alkali metal or alkaline earth metal alcoholates, amides or hydrides. The alkali metals or alkaline earth metals themselves or their amalgams are also suitable, as well as alcoholic solutions of the alcoholates.

Particularly well suitable solvents, having the additional side effect of accelerating the cyclization reaction, are among the carboxylic acid amides: dimethyl formamide (DMF), dimethylacetamide (DMAC), N- methylpyrrolidone (NMP). A particularly well suited amide of phosphoric acid is hexamethyl phosphoric triamide.

When using as solvent a product of the sulfoxide or sulfone group, dimethyl-sulfoxide (DMSO) and sulfolane are preferred.

A macrocyclic polyether suitable as solvent is, for example, cyclohexyl-l 8-crown-6-ether The amides of carboxylic acids and phosphoric acid, the sulfoxides, sulfones or macrocyclic polyethers may be used in admixture to other solvents. The quota of these latter may then amount up to 50 7:, preferably up to 30 7c. Suitable mixture components are, for example, methanol, diethyl ether, acetonitrile, and benzene.

Generally, the cyclization is performed at a temperature of from 0 to 150C, preferably between 15 and C, without pressure and either continuously or discontinuously. The solvent is generally used in an excess of from 10 1 to 10,000 1 based on theinitial ester. The solvents may be used again after re-cyclization.

The reaction takes place with a high degree of selectivity 70) and a high space-time-yield 300 g/ 1 .hr). Crystallized products of a highgrade purity are obtained. The reaction may be represented, for example, by the following formulae, providing that-yacetobutyric acid methyl ester is used:

3 Particularly suitable initial materials are: 'y-acetylbutyric acid methyl ester, y -acetyl-y-phenyl butyric acid methyl ester, y-acetyl-y-propyl butyric acid ethyl ester.

The reaction may be performed, for example, as folacylbutyric acid ester, dissolved in a determined quan-. lows: tity of solvent. During this phase the temperature is To a first introduced mixture of the condensation checked by cooling, if necessary. The reaction is folagent and of the solvent, the ester to be submitted to lowed up by means of a gas chromatographic analysis. cyclization iscontinuously added, while stirring vigor- As long as some free condensation agent is still present, ously, at such a speed that the concentration in free the reaction takes place practically spontaneously. ester is low. Since the solvents according to the inven- Once the reaction is terminated, the solvent is elimition cause the reaction to speed up considerably, the nated in vacuo, the residue digested with ether, disaddition may take place very fast and the space-time solved in a small quantity of water and the solution yields of from 600-1000 gr/1.hr. are obtained. As soon acidified by concentrated hydrochloric acid. When as a quantity of ester equimolar to the condensation using ether or methanol as solvent (examples 1 and 2), agent is added the solvent is eliminated in vacuo. The a yellow-brownish oil separates upon acidifying the salt, obtained as residue, is dissolved in a determined aqueous alkali metal salt solution, from which a small quantity of water and the solution is then acidified by a amount of dihydroresorcinol is obtained by means of a concentrated acid. During the cooling process the cyccumbersome crystallization. The yield is abt. 37 7c, lic diketones precipitate in their pure crystal form. It is 39 resp. 14 7c. 9 further possible to obtain a small percentage by extrac- However, the reaction being performed in DMF, tion of the aqueous mother liquor. The net yields after DMSO or DIVIAC, a practically pure crystalline dihyre-crystallization amount to 95 7:. drorcsorcinol is obtained in a high yield. The result is The following examples illustrate the invention: similar with the use of mixtures of DMF/methanol' and EXAMPLES 1-2 A mixture of condensation agent and solvent is first introduced into a 1 ltr- 4-necked flask, equipped with a and a reflux condenser. To this mixture is added dropwise uniformly and over a definite period an equimolar quantity calculated on the condensation agent of DMF/diethyl ether.

Additionally, it is possible to extract a small quantity from the aqueous phase by methylene chloridef The yield amounts to 95 7: after recrystallization.

Examples 1 8 Cyclization of y-ncetylbutyric acid methyl ester (y/\BM) to yield dihydroresorcinol Example Solvent (1) -ABM Condcnsationreaction time Kind ml Solvent agent min g/ml Kind g l diethyl- 450 48/50 NaOCH 480 ether 2 methanol 350 48/50 NaOCl-L 20 360 3 DMF 250 48/50 NaOCH 20 30 4 DMF 350 48/100 NaOCH 20 0. 5 DMF 250 72/70 NaOCH 3O 6 DMSO 250 48/100 NAOCH 20 60 7 DMSO 250 48/100 NaH 10 60 8 DMAC 250 48/100 NaOCH 20 60. 9 DMF/ 240 48/80 NaOCH 20 60 Methanol 5 1 l0 DMF/ 240 48/80 NaOCH 20 60 diethylether Examples temperature H O conc.HCl yield space-lime melting yield point "C ml ml 7: ot'lheory g/l-h "(I 1 2534.6 5O 46 37 3 103 2 25 5O 31 14.1 2 103 3 25 55 31 95.3 215 104 4 25 55 31 98.0 105 5 24 8O 46 94.0 180 103 6 23 50 30.5 95.6 89 104 7 25 50 30 96.5 90 104 8 25 55 31 92.0 86 105 9 25 50 32 85.0 85. 103 10 25 50 31 93,0 94 104 "first introduced:

g-y-ABt l per ml of solvent in dropping funnel "H- O added to dissolve the dihydroresorcinol;

*conc. hydrochloric acid for precipitation of the cyclic dione "yield Lifter recrystallization from benzene R i Examples l l. l2 Cycllzauon of y-Acetylcarboxylic acid H,,C-C H(CH -C esters OCH Example R Solvents Estcr/DMF Condcnsationreaction(-) DMF agent time NuOCH ml g/ml g min ll CH 250 53/l00 60 12 d. 250 73/l00 20 60 Example temperature H O conc.HCl yield space-time Fp. Blg.-pt.

yield "C ml ml 7: d. Theory g/l-h C C/8 torr ll 35 60 30.5 94.5 100 I35 12 35 6O 95.5 145 ll" What is claimed is: 1. Process for preparing cyclohexanediones-( 1,3) having the formula R RR l a ll H wherein the individual radicals R may be identical or different and represent each a hydrogen atom, an alkyl group or an aryl group by reaction of a 'y-acyl-carboxylic acid ester having the formula wherein R has the aforesaid meaning and R is an alkyl group or an aryl group, with a strongly basic condensation agent in the presence of a solvent consisting essentially of a member of one of the following groups.

a. carboxylic acid amides having the formula wherein the individual radicals R may be identical or different and represent each a hydrogen atom, an alkyl group or an aryl group b. phosphoric acid amides having the formula wherein the individual radicals R may be identical or different and represent each an alkyl group or an aryl group,

c. sulfoxides and sulfones having the formula R-S-R and R-'SR ll ll 0 0 wherein the individual radicals R may be identical or different and represent each an alkyl or an aryl group, and d. macrocyclic polyethers, said solvent'being removed from the reaction product upon completion of the cyclization reaction and thereafter acidifying the reaction product to obtain said cyclohexanediones.

2. The process of claim 1 wherein the solvent consists of at least 50% of said (a) carboxylic acid amides, (b) phosphoric acid amides, (c) sulfoxides and sulfones, and (d) macrocyclic polyethers.

3. Process according to claim 2, which comprises using alkali metals or alkaline earth metals or of their alcoholates, amides or hydrides as condensing agents.

4. Process according to claim 2 which comprises using dimethyl formamide, dimethyl acetamide or N- methylpyrrolidone as solvent.

5. Process according to claim 2 which comprises using hexamethyl phosphoric triamide as solvent.

6. Process according to claim 2 which comprises using dimethylsulfoxide as solvent.

7. Process according to claim 2 which comprises using sulfolane as solvent.

8. Process according to claim 2 which comprises using cyclohexyl-l8-crown-6-ether as solvent.

9. The process as defined in claim 2 and wherein the solvent is used in an excess from 10:1 to 10,000:l based on the amount of initial ester.

10. The process as defined in claim 2 wherein the 'yacyl-carboxylic acid ester is reacted with a strongly basic condensation agent selected from the group consisting of alkali metals, alkaline earth metals, and their alcoholates, amides and hydrides wherein the reaction is carried out in the presence of a solvent containing at least 50% of a carboxylic acid amide selected from the group consisting of dimethylformamide, dimethylacetamide, N -methylpyrrolidone, hexamethyl phosphoric triamide, dimethyl sulfoxide, sulfolane and cyclohexyll8-crown-6-ether said solvent is used in an excess from 10 to l to 10,000 to 1 based on the amount of initial ester and the reaction is carried out at a temperature between 0 and C.

11. The process for preparing diones( 1,3) having the formula cyclohexanewherein the individual radicals R may be identical or different and each represents a hydrogen atom, an alkyl group or an aryl group, by reaction of a 'y-acyl-carboxylic acid ester having the formula wherein R has the aforesaid meaning and R is an alkyl group or an aryl group, with a strongly basic condensation agent in the presence of a solvent comprising at least 50% of a member of one of the following groups:

a. carboxylic acid amides having the formula wherein the individual radicals R may be identical or U different and each represents a hydrogen atom, an alkyl group or an aryl group, i b. phosphoric acid amides having the formula wherein the individual radicals R may be identical or i different and each represents an alkyl group or an aryl group, c. sulfoxides and sulfones having the formula wherein the individual radicals R may be identical or 7 different and each represents an alkyl or an'aryl group, and d. macrocyclic polyethers; and up to 50% of a solvent which is a member selected from the group consisting of methanol, diethyl ether, acetonitrile and I benzene,

said solvent being removed from the reaction prod uct upon completion of the cyclization reaction and thereafter acidifying the reaction product to obtain said cyclohexanediones. 

1. PROCESS FOR PREPARING CYCLOHEXANEDIONES-(1,3) HAVING THE FORMULA
 2. The process of claim 1 wherein the solvent consists of at least 50% of said (a) carboxylic acid amides, (b) phosphoric acid amides, (c) sulfoxides and sulfones, and (d) macrocyclic polyethers.
 3. Process according to claim 2, which comprises using alkali metals or alkaline earth metals or of their alcoholates, amides or hydrides as condensing agents.
 4. Process according to claim 2 which comprises using dimethyl formamide, dimethyl acetamide or N-methylpyrrolidone as solvent.
 5. Process according to claim 2 which comprises using hexamethyl phosphoric triamide as solvent.
 6. Process according to claim 2 which comprises using dimethylsulfoxide as solvent.
 7. Process according to claim 2 which comprises using sulfolane as solvent.
 8. Process according to claim 2 which comprises using cyclohexyl-18-crown-6-ether as solvent.
 9. The process as defined in claim 2 and wherein the solvent is used in an excess from 10:1 to 10,000:1 based on the amount of initial ester.
 10. The process as defined in claim 2 wherein the gamma -acyl-carboxylic acid ester is reacted with a strongly basic condensation agent selected from the group consisting of alkali metals, alkaline earth metals, and their alcoholates, amides and hydrides wherein the reaction is carried out in the presence of a solvent containing at least 50% of a carboxylic acid amide selected from the group consisting of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, hexamethyl phosphoric triamide, dimethyl sulfoxide, sulfolane and cyclohexyl-18-crown-6-ether said solvent is used in an excess from 10 to 1 to 10,000 to 1 based on the amount of initial ester and the reaction is carried out at a temperature between 0* and 150*C.
 11. The process for preparing cyclohexanediones(1,3) having the formula 